Fort Worth Energy Code Multifamily: 2015 IECC, ASHRAE 90.1-2013, and When to Study First

If you are building multifamily inside the City of Fort Worth, the trap is the opposite of the one in Austin. Fort Worth adopted the 2021 International Code Council codes effective April 1, 2022, so teams assume the 2021 IECC came with them. It did not. The City says it will retain the 2015 International Energy Conservation Code, with Fort Worth amendments, and it accepts ASHRAE 90.1-2013 as the alternative. Teams get caught when they design and document to a newer IECC or ASHRAE year than the City enforces, copy a Dallas, Houston, or San Antonio package from down the road, or miss the Fort Worth rule that air and duct leakage testing must be done by an independent third party.

This page is the Fort Worth Energy Code door for multifamily developers. For the statewide Texas commercial code path (the 2015 IECC floor, ASHRAE pairings, and why mid-rise is not HERS-first), see ASHRAE COMcheck Texas multifamily. For the Texas study door, see energy code feasibility study Texas. Other Texas city doors already live: Houston Energy Code multifamily, Austin Energy Code multifamily, Dallas Energy Code multifamily, and San Antonio Energy Code multifamily. Program, testing, and modeling context: ENERGY STAR Multifamily New Construction, blower door testing for multifamily buildings, and multifamily energy modeling.

What Code Applies in Fort Worth Right Now

Per the City of Fort Worth Development Services Building and Energy Codes and Permits pages and the energy code ordinance itself (primary sources; confirm with the City before you file):

• The City adopted the 2021 International Building, Residential, Mechanical, Plumbing, Fuel Gas, Fire, and Existing Building Codes, effective April 1, 2022, with the exception of the energy code. The City's words: it will retain the 2015 International Energy Conservation Code.
• Ordinance 22520-12-2016, approved by City Council on December 6, 2016 and effective January 1, 2017, adopted the 2015 IECC with local amendments as the Fort Worth Energy Code (City Code Chapter 7, Article II, Sections 7-41 through 7-44).
• For the state energy mandate, the City says the two codes that can be used are the 2015 IECC and ASHRAE 90.1-2013. Either can be used, but once selected it must be used in its entirety.
• The City notes it typically adopts new codes every other ICC cycle, so check the energy code edition on your filing date rather than assuming it moved with the building code.

That makes Fort Worth the outlier among ECC's Texas city doors. Houston, Dallas, and San Antonio enforce the 2021 IECC with ASHRAE 90.1-2019 options, and Austin moved to the 2024 IECC and ASHRAE 90.1-2022 on July 10, 2025. Fort Worth sits on the same 2015 IECC edition as the statewide Texas floor, with its own amendments on top. Use the City's pages and adopted ordinance as the source of truth, not a blog summary.

Residential vs Commercial Split for Multifamily

The 2015 IECC draws the line by building type and height. Group R-2, R-3, and R-4 buildings three stories or less above grade plane fall under the residential provisions. Taller apartment buildings, and the nonresidential portions of any building, fall under the commercial provisions, where the 2015 IECC or ASHRAE 90.1-2013 applies.

• Mixed-use and podium projects. Retail, amenity, lobby, corridor, and parking areas follow commercial documentation even when the team thinks of the job as "apartments."
• One code per filing. Because the City requires the chosen code to be used in its entirety, a commercial portion is either a 2015 IECC filing or an ASHRAE 90.1-2013 filing, not a mix of the two.

That split decides whether you are looking at residential envelope tables, testing, and an ERI or performance path, or a commercial package with COMcheck reports or whole-building modeling. Confirm it with Fort Worth plan review before anyone models.

Fort Worth Commercial Documentation

The City says a complete energy code submittal depends on the scope of work and can include up to four separate parts:

1. Envelope compliance, required for heated or cooled buildings when exterior walls, windows, or doors are built or changed.
2. Interior lighting compliance, required when interior lighting is added or altered.
3. Exterior lighting compliance, required when exterior lighting is added or altered.
4. Mechanical compliance, required whenever heating, ventilating, air conditioning, or water heating is installed or altered.

The City points to COMcheck from the U.S. Department of Energy as the most common program for those reports, and says approval of an alternate method or program goes through the Fort Worth Building Code Administrator. The COMcheck version and code year you select have to match the code you declared: 2015 IECC or ASHRAE 90.1-2013.

Fort Worth Amendments Multifamily Teams Miss

Ordinance 22520-12-2016 changes several 2015 IECC sections that hit apartment and mixed-use projects:

• Independent third-party air leakage testing (R402.4.1.2). Mandatory air leakage testing may only be performed by individuals certified by national or state organizations approved by the building official. They must be an independent third party and may not be employed by, or have any financial interest in, the company that builds the structure.
• Independent third-party duct testing (R403.3.3). The same independence rule applies to duct leakage testing.
• Energy Rating Index (Table R406.4). Fort Worth replaces the ERI table for climate zone 3 with a stepped schedule ending at a maximum ERI of 59 on or after September 1, 2022.
• Performance software (R405.6.2). The City lists acceptable simulation tools and allows other RESNET BESTEST accredited programs that can produce the required report, at the building official's discretion.
• Energy certificate (R401.3 and R103.2). Residential plans carry a representation of the Fort Worth energy certificate, listing insulation, window U-factor and SHGC, duct and envelope leakage, and equipment.
• Exposed foundation insulation (C303.2.1 and R303.2.1). Because of Fort Worth's very heavy termite classification, designs with exterior insulation of basements or slabs shall not be used.
• Fenestration and openings (C402.4.1, C402.4.1.1). Vertical fenestration stays capped at 30 percent of gross above-grade wall area, and roll up or folding walls that open conditioned space to patios or sidewalks are not accepted unless each opening has an HVAC kill switch and the tenant space and zoning conditions in the ordinance are met.
• Vestibules (C402.5.7). Fort Worth's vestibule exceptions include doors opening directly from a dwelling unit or sleeping unit, doors from spaces under 3,000 square feet, and doors with a tested air curtain.

Treat those as path facts, not a design checklist. The adopted ordinance text is the set of numbers to design against.

Low-Rise Apartments: Paths and Testing

Where the residential provisions apply, the 2015 IECC paths are prescriptive (including the UA alternative), simulated performance, and ERI, with Fort Worth's ERI ceiling of 59 in climate zone 3. Fort Worth also lets a building certified by a national, state, or local accredited energy efficiency program, and determined by the Energy Systems Laboratory to meet the code, be considered in compliance at the code official's option, and it treats EPA ENERGY STAR certification of energy code equivalency as compliant. Whatever the path, plan the blower door and duct testing around a tester who is truly independent of the builder, because a test by the wrong party is a test you run twice.

Proof From ECC Studies (Method, Not Fort Worth Invoices)

ECC does not publish a Fort Worth or Texas dollar-per-square-foot average, and we do not have a Fort Worth energy-code invoice to present as your number. We cite other studies as proof of method, and we label them that way.

On our 267-unit Cromwell, CT study (CS68), two buildings up to six stories (272,036 square feet) were filed on IECC commercial provisions using ASHRAE 90.1-2019 Appendix G. The recommended all-electric tier came in at about $35.23 per square foot net and captured a $1,500 per unit Energize CT incentive ($400,500). Those are Connecticut commercial-code outcomes on a newer ASHRAE year than Fort Worth enforces, not Fort Worth invoices. They show the order: lock the path, rank the packages, then document the winner.

On a 112-unit Revere, MA study (CS57), a seven-story mixed-use building kept dwelling units on a Massachusetts Stretch HERS path and still called for a COMcheck report for all common and support areas, plus ASHRAE 62.1 ventilation calculations and lighting power density calculations. The recommended ductless package landed at about $42.52 per square foot net. Those are Massachusetts outcomes. We cite them as proof that mixed-use paperwork splits before modeling hours, not as a Fort Worth price.

Common Mistakes on Fort Worth Multifamily Energy Filings

• Assuming the 2021 IECC came with the 2021 codes. Fort Worth adopted the 2021 building-related codes effective April 1, 2022, but kept the 2015 IECC.
• Documenting to the wrong ASHRAE year. Fort Worth lists ASHRAE 90.1-2013, not the 90.1-2019 used in Houston, Dallas, and San Antonio or the 90.1-2022 used in Austin.
• Mixing codes inside a filing. The City requires the 2015 IECC or ASHRAE 90.1-2013 to be used in its entirety once selected.
• Using a builder-affiliated tester. Air leakage and duct testing must be done by an independent, certified third party with no financial interest in the builder.
• Specifying exterior slab or basement insulation. Fort Worth bars it because of the termite classification, so the foundation detail has to change early.
• Leaving the lighting reports off. Interior and exterior lighting compliance are separate parts of the Fort Worth submittal whenever lighting is added or altered.
• Buying COMcheck or ERI hours before the path is locked. The study should settle residential vs commercial, which code you will declare, and the ERI or performance target, then the paperwork follows.

When to Study First

Settle the Fort Worth path before anyone buys REScheck, COMcheck, ERI, or whole-building modeling hours:

1. Confirm the permit address is inside the City of Fort Worth and on the energy code in force for your filing date (2015 IECC with Fort Worth amendments since January 1, 2017, retained through the 2021 code adoption)
2. Lock the residential vs commercial split (three stories or less for Group R-2 / R-3 / R-4 on the residential provisions, and commercial documentation for nonresidential areas)
3. For each commercial portion, declare one code for the whole filing: 2015 IECC or ASHRAE 90.1-2013, and list which of the four compliance parts the scope triggers
4. For residential portions, pick the path (prescriptive, performance, or ERI at 59) and line up an independent, certified third-party tester for air and duct leakage
5. Model envelope and HVAC packages side by side against that path, including ENERGY STAR Multifamily New Construction where you plan to enroll
6. Produce the COMcheck reports, energy certificate, and test reports against the locked plan

That comparison is what a free feasibility study produces. For the Texas study method, see energy code feasibility study Texas. For how modeling works on apartment buildings in general, see multifamily energy modeling. If the path is already chosen and you need COMchecks, modeling, inspections, or testing, see ECC services.

Bottom Line

The Fort Worth energy code for multifamily is the 2015 IECC with Fort Worth amendments (Ordinance 22520-12-2016, effective January 1, 2017), kept in place when the City moved its other codes to the 2021 editions on April 1, 2022. Commercial portions use the 2015 IECC or ASHRAE 90.1-2013 in its entirety, documented in up to four parts. Residential portions add independent third-party air and duct testing and an ERI ceiling of 59. This is the Fort Worth city-code door, not the statewide Texas code-path page, not the Houston, Austin, Dallas, or San Antonio city doors, and not the Texas study door. Lock the split, the code, and the targets first, then buy the paperwork that matches the plan.